Electrodermal activity and heart rate were recorded during rest, simple tones, and a reaction time task in 43 subjects with obsessive compulsive disorder and 30 boys with disruptive behavior disorders who had lumbar cerebrospinal fluid drawn during the same week. Partial correlations controlling for age and sex showed that in the obsessive group metabolites of serotonin and dopamine, but not of norepinephrine, were positively correlated with electrodermal responsivity, most consistently in the reaction time task. This was not replicated in disruptive boys. Adrenocorticotropic hormone was positively related to electrodermal activity and heart rate throughout the session. The results for the obsessive subjects suggest that nigrostriatal dopamine turnover and central serotonin turnover affect electrodermal activity, generally confirming and extending conclusions from pharmacological studies. Diagnosis may affect these relationships.